Closed rotors in which a flow channel is defined by the rotor blades, a rotor disk carrying these rotor blades, and a cover disk connected to the rotor blades are known, for example, from DE 198 33 033 A1 (U.S. Pat. No. 6,255,752 B1) which shows, in FIGS. 8 to 13, cover disks with different meridional cross sections. As can be seen in particular, the wall thickness decreases along the profile mean line of the meridional cross section of cover disks of this kind, generally continuously from a suction port to a flow outlet.
DE 37 09 518 C2 and DE 41 13831 A1 disclose closed rotors with a cover disk in which an outer surface of the cover disk remote of the flow channel has a radial offset adjoined by a conical portion of constant wall thickness so that there is a local maximum in the wall thickness of the cover disk between the suction port and the flow outlet in the radial offset. However, this is not discussed in DE 37 09 518 C2 or in DE 41 13831 A1.
In known cover disks, high stresses disadvantageously occur at unfavorable structural points.
Therefore, it is the object of the present invention to provide an improved cover disk.